Phase transformation.



PATENTED OUT. 4, 1904.

A. D. LUNT. PHASE TRANSFORMATION.

APPLICATION FILED JULY 31, 1900.

N0 MODEL.

Fig. 1.

Jnventor: Alexander D. Lunt Witnesses UNITED STATES Patented October 4,1904.

PATENT OEEIcE.

ALEXANDER D. LUNT, OF SCHENECTADY, NEW YORK, ASSIGNOR TO THE GENERALELECTRIC COMPANY, A CORPORATION OF NEIV YORK.

PHASE TRANSFORMATION.

SPECIFICATION forming part of Letters Patent No. 771,314, dated October4, 1904.

Application filed July 31,1900. Serial No. 25, 118. (N model.)

To all whom; it may concern:

Be it known that I, ALEXANDER D. LUNT, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New 5 York,have invented certain new and useful Improvements in PhaseTransformation, of which the following is a specification.

My present invention relates to amethod of transforming three-phasecurrent into twelve- I phase current, or the reverse, and is ofparticular value for use in connection with rotary converters in whichthe armature heating is less the greater number of phases there are onthe alternating-current side of the ma- 5 chine.

In practice I make use of three transformers, each of which is providedwith one winding connected to the three-phase system and three otherwindings connected to the twelvephase system. In allthere are ninewindings connected to the twelve-phase system, and these windings are sointerrelated that their electromotive forces may be represented by adouble delta superposed upon a double Y.

S A better understanding of the invention will be had by reference tothe following description, taken in connection with the accompanyingdrawings, while the points of novelty of the invention will be set forthin 3 the claims appended hereto.

Figure 1 is a representation of my invention, and Fig. 2 a diagram ofelectromotive forces.

I The phase transformation is performed, preferably, bya set oftransformers having primary windings differing in number from thesecondary windings. In Fig. 1 three transformers are shown,havingprimary windings AB C, connected, respectively, to three- 4 phase mains,each primary being provided with three secondaries, two of which areidentical in current-carrying capacity and number of turns, while thethird has a slightly larger number of turns. Of course if twelve-phasecurrent is to be converted into three-phasethe windings will be reversedin function, those connected to the three-phase mains being theirsecondaries and the others primaries.

In the present embodiment of the invention all of the secondaries areconnected to a rotary converter in such manner as to supply twelve-phasecurrents thereto. Fig. 1 illustrates this mode of connection in diagram,while Fig. 2 represents the electromotive forces acting in the systemand by an arrangement of corresponding lettering is of assistance inexplaining the connections in Fig. 1.

For convenience the armature-winding of the converter is represented inFig. 2 by the circumscribing-circle D, while the points of connection ofthe winding are indicated by the radial lines which emanate therefrom atregular intervals, as shown, and which are numbered to correspond withthe similarly-numbered taps connected to the conventional representationof the armature-winding in Fig.

1. The phases of the different electromotive forces acting upon thiswinding are indicated by the combination of radii and triangles withinthe circumference of the circle in Fig. 2.

In making up the connections between the transformers and theconverter-armature the first step is to connect in delta three of thesecondaries of the several transformers, this connection being made inthe ordinary manner. In the drawings this delta connection starts at 1",through the transformer-winding to 2", then through atransformer-winding on the next phase from 3 to A", then through atransformer-winding of the remaining phase from 5" to 6", and then backto 1". This connects the electromotive forces of the windings in delta,and from points in the connections joining the transformer-windingsleads eX- tend to points on the converter-a1mature separated from eachother by one-third of the polar pitch. Referring to the diagramrepresenting the converter-armature,it will be seen that the connectionsfrom the secondary terminals 9 1 2" lead to the taps l to 5, which inFig. 2 connect to points joined by the chord designated,correspondingly, as l" 2". In like manner the secondary 3" 4" isconnected to the taps 5 to 9 spanning the corresponding chord 3" A",while the remaining secondary of the delta is connected across the chord6 thus completing one delta arrangement of electromotive forces actingupon the converter-armature.

The next step is to connect up another delta, but in this case with twoof the sides reversed in order to obtain a six-pointed-star arrangementrepresented by the two superposed and relatively reversed deltasindicated in Fig. 2.

To enable the connections to be readily traced, it may be stated thatparallel sides of the two deltas should have the same polarity at theircorresponding ends. Thus, for example, the sidel 2 of one delta and theparallel side 1 2 of theother delta should have theirsimilarly-extending ends of the same polarity.

The Figs'l 2, as applied to the secondaries in transformer A, indicatethe opposite polarit'ies, while the exponents a b 0 distinguish betweenthe respective secondaries. A similar lettering is used in connectionwith the other two transformers. In making all connections between thetransformer-secondaries in Fig. 1 a convenient guide may therefore besecured by similarly lettering the diagram of electromotive forces inFig. 2. Thus the secondary connected to the taps 1 to 5 across the chord1 2 has its terminal 2 at the left-hand end of the winding, asindicated. The similar secondary 1 2 should therefore have itscorresponding terminal 2 of the same polarity indicated by theapplication of the referenceletters 2 to the left-hand terminal. In asimilar manner all the parallel chords aredesignated by correspondingreference letters, whereby the proper sequence of connections may bereadily made by consulting the diagram thus lettered. To connect up thesecond delta, the connections through the varioustransformers willtherefore start at 1", through the winding to 2, then through thewinding 5 6, and then through the remaining winding 3 4?, back to theterminal 1, thus completing a reversed delta, Three connections leadtherefrom and are joined to corresponding points of theconverter-armature, as indicated by the taps 3 7 11. Thus, toillustrate, the tap 7 (shown in Fig. 2 as leading to the intersectingends 2 and 5 of two chords) is connected to theircorrespondingly-lettered transformer-terminals in Fig. 1. When it isunderstood that the apexes of one delta lie midway between theconnections of the apexes of the other delta no difliculty will be foundin making the connections to the proper points in the convertedarmature.

To complete the twelve phase connections to the rotary converter, theremaining secondary windings are connected, so that each secondary spansa diameter and is symmetrically connected with relation to the othersecondaries, whereby the points of connection of one secondary aredisplaced by an angle of sixty degrees from each of the othersecondaries. The points of connection are, however,

chosen so as to lie midway between those of the double deltas, therebyconstituting therewith a twelve-phase relation of electromotive forcesacting upon the armature. In making the connections it is only necessaryto remember that the double-Y connections, represented in the drawingsby diameters, magnetize in the same direction as the chordsparalleltheretothat is to say, the adjacent ends of each diameter and its twoparallel chords should be of the same polarity. Thus the adjacent ends 2and 2 of two parallel chords are connected, respectively, to windingswhose left-hand terminals are similarly designated. The COll across thediameter 1 2 must magnetize in'the same direction as the parallel chordsand is therefore connected with its left-hand end 2 to the tap whichliesbetween the connections of the endsof the chords parallel' to thisdiameter. The remaining connections will readily be understood withoutfurther explanation.

It will be evident that the currents flowing in the windings of thephase-changing transformers are normally in phase with the electromotiveforces generated in the'respective windings. The windings therefore arenot burdened with Wattless currents and may thus be made smaller thanwould benecessary in a system of phase transformation in. which a flowof wattless current is inherent.

Although for purposes of explanation Ihave assumed that three-phasecurrent is converted by the apparatus showninto twelve-phase current andsupplied toarotary converter, it will of course be obvious that thereverse operation is quite within my invention. In the latter casedirect current would be-fed into the rotary converter, by which it wouldbe transformed into twelve-phase current and then by the arrangement oftransformers shown into three-phase current. The exact scope ofmyinvention is, however, to be determined not by means of the abovedetailed description, but by reference to the following claims.

What I claim as new, and desire tosecure by Letters Patent of the UnitedStates, is

1. The method of producing twelve-phase current, which consists incombining like phase electromotive forces derived from one phase of athree-phase system,with like phase to flow in phase with saidelectromotive forces,

and deriving twelve-phase current therefrom.

2. The method of producing twelve-phase currents which consists insetting up a plurality of three-phase electromotiveforces, combin ingsaid electromotive forces so astoform a double delta and a double Y, andthen deriving twelve-phase currents from the combination ofelectromotive'forces.

IIO

ing a plurality of electromotive forces in a double-delta relation,associating other electromotive forces in a relation represented by adouble Y, and through the medium of the resultant electromotive forces,transferring energy between a direct-current system and analternating-current system.

In witness whereofI have hereunto set m'y\ hand this 30th day of July,1900.

ALEXANDER D. LUNT.

W'itnesses:

BENJAMIN B. HULL, JAMEs J. HIGGINS.

